The present invention relates to a semipermeable membrane made from polyether ketones and to a process for its production.
Since the introduction of asymmetrical membranes from cellulose acetate (by Loeb and Sourirajan, see S. Sourirajan, Reverse Osmosis, Logos Press, London 1970) and from hydrophobic polymers (U.S. Pat. No. 3,615,024), numerous membranes have been developed and proposed, in particular for separating low- and macromolecular constituents dissolved in water. The structures and possible applications of these membranes have been described in the literature (Desalination, 35:5-20 (1980)), and the membranes have also been successfully employed for industrial or medical uses.
Many of the described membranes possess properties which render them particularly well suited for solving specific problems. Due to the differing chemical compositions and structural configurations of the individual membranes, the optimum suitability of each membrane is limited to very specific separation problems. This leads to the basic necessity of having to provide a new membrane for each new problem.
EP 082 433 gives a comprehensive survey on the advantages and disadvantages of known membranes. Hydrophilic asymmetrical membranes made of cellulose acetate exhibit, for example, satisfactory antiabsorptive properties, but possess inadequate thermal and chemical stability. Membranes made of polysulfones or similar polymers are distinguished by good thermal and chemical stability, but they are sensitive to the action of organic solvents.
Membranes made of cellulose reclaim material have both a hydrophilic character and resistance towards solvents; however, they are easily hydrolyzable in acid or alkaline media, and can be easily attacked by microorganisms.
DE 33 21 860 discloses membranes of partially-sulfonated polyether ketone which are chemically stable. These membranes are not dissolved as a result of the action of organic solvents, such as acetone or tetrahydrofuran (THF), but they swell considerably, which changes their membrane properties irreversibly.